WINNIPEG – The fear of phosphorous moving into waterways may be the biggest obstacle to expansion of the prairie hog industry.
Water pollution can result from high phosphorus concentrations found in hog manure applied to fields.
The two major nutrient components in hog manure are phosphorus and nitrogen. Prairie farmers have a number of cropping rotations capable of consuming high amounts of nitrogen, so that element is less of a concern.
Phosphorus is the real culprit. Liquid hog slurry is heavy and bulky. It’s not economically viable to transport it far from the source as a fertilizer product. The economics turn negative once the manure is moved more than a few kilometres whether by truck, trailer or pipeline.
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So, while most of the excess nitrogen is used by crops within that tight radius around hog barns, the phosphorus accumulates and contributes to potential problems.
It’s long been understood that the solids in hog manure hold most of the phosphorus, while liquids hold the nitrogen. If you can successfully separate solids from liquids, you can separate phosphorus from nitrogen.
Each segregated nutrient would then be a more concentrated form and can be transported more economically.
If a hog operation can offer a lighter weight solid substance with a documented high phosphorus rating, there is a better chance of finding commercial customers who can incorporate it into their farming operations.
Even if it doesn’t turn a major profit, a high concentrate phosphorus solid may at least bring enough cash to pay for its travel to greener pastures elsewhere.
To a lesser degree, the liquid nitrogen component also increases in commercial value because it is now a more concentrated liquid.
But segregating solids from liquids has remained an elusive trick, according to Daryl Heit of United Livestock Systems in Bowden, Alta.
“Until very recently, dewatering hog manure on a commercial scale has been difficult,” says Heit, who was in Winnipeg last month to introduce a new dewatering press at the 2006 Hog & Poultry Days.
The machine displayed in Winnipeg is the Parkson DynaPress Manure Dewatering Press DP. It is the first of its type in Canada.
“Conventional screw press dewatering systems used today only remove 30 to 35 percent of the solids from the liquid,” said Heit. “The system we’ve started importing removes 90 to 95 percent of the solids from the liquid.
“Most phosphorus remains with the solid portion of the manure. That means we can recover 90 to 95 percent of the phosphorus in the solid material that comes out the gate.
“Only four to five percent of the phosphorus remains in the liquid. In effect, we can now separate phosphorus from nitrogen in hog manure.”
In most setups, the phosphorus is about 25 percent dry when it emerges from the basic DynaPress Model DP dewatering press.
The Parkson company calls it cake and it is dry enough that it can be stacked with front-end loaders without risk of leeching or runoff, Heit said.
Although the phosphorus-laden solid cake is now easier to handle and move, Heit said it will still be necessary to find markets for the product.
“There are a number of options, such as tree nurseries. Solids with phosphorus may still be a problem, but it’s a much easier problem to solve in this form, because now you can move it around.”
The DynaPress can produce solids up to 60 percent dry, which further decreases weight and increases the market range for the phosphorus cake.
Heit said raw slurry enters the dewatering press through a suction pump at the inlet port. It goes through a mixer that blends the slurry with a polymer powder.
The polymer particles bind to the suspended solids in the slurry. The rate and strength of the polymer additive is based on a manure analysis done in advance to determine phosphorus levels.
“Usually, you only do this analysis once,” Heit said. “But if there’s a drastic change in the feed ration or the overall operation of the barn, then it’s necessary to do another analysis.”
The polymer enters a continuous feed nozzle. As long as slurry flows in, polymer is injected.
The slurry then runs through a network of tubes to slow it down and give the polymer additive more time to bond with the phosphorus. The pipes flow into the dewatering press chamber, where the separation of solids and liquids occurs.
The circular dewatering chamber accepts the slurry-polymer blend and forces it between two parallel stainless steel filter plates that rotate slowly at three revolutions per minute.
The perforated filter plates allow liquid to pass through as the drying solids continue their 270-degree trip around the press chamber, continually losing water as they approach the exit gate.
The frictional force of the slowly rotating plates and the amount of time the slurry is in the chamber determine phosphorus cake dryness at the exit.
“If the gate is open, there is less backpressure and the manure moves through quicker, but it’s not as dry,” Heit said.
“We have an air valve to control the gate. The more we close the gate, the more back pressure we create and the slower the manure moves. That gives us a drier cake coming out the gate.”
Gravity allows the nitrogen-rich liquid to trickle from the dewatering press, where it is collected and pumped to its own storage tanks.
At this point, the producer has the option of applying the liquid as fertilizer or refining it to a higher concentrate.
“With more filters, the liquid can be cleaned to meet environmental standards for discharge directly into rivers and streams. But this does require further chemical treatment.”
Heit said Parkson is installing a major dewatering plant at a 13,000-cow dairy operation in Israel. It will clean recovered water to a standard that it can be discharged directly into the environment.
The skid-mounted DynaPress model DP Heit displayed in Winnipeg is the smallest unit built by Parkson.
“It does 20 gallons per minute. That should handle up to a 300 or 400 sow farrow-to-finish operation. Depending on options, the price runs about $70,000 US.
“We have bigger machines on skids that can handle up to a 1,500 sow farrow-to-finish. That’s running it just eight hours a day.”
The self-contained, skid-mounted DynaPress is totally enclosed to reduce odours and corrosive exposure to nearby equipment. It is ready for immediate hookup once delivered.
The operator needs to make only three adjustments to custom program DynaPress to a particular hog operation: required polymer dosage based on manure analysis; desired solid capture rate and desired dryness of the cake solids.
For more information, contact Daryl Heit at 403-224-3454.
